Demonstrate Your Impact: Metrics

Bibliometrics are statistics used to measure the impact of authors, articles, and publications. Researchers and publishers have developed many different algorithms and measures to capture and communicate the importance of scholarly works. Metrics might be displayed differently in different databases. Additionally, bibliometrics may be discipline specific and could vary widely from one subject area to another.

Glossary of Metrics and Impact Measures

Below is a brief glossary of common metric types and ways to measure impact.

Author-Level Metrics

h-index: The h-index, or Hirsch index, measures the productivity (number of articles published) and the impact (number of citations) of an individual researcher or author. It indicates the number of publications n that were cited at least n times. For example, an author with an h-index of 5 has published 5 papers, each of which has been cited by others at least 5 times. 

g-index: The g-index is a a variant of the h-index that gives more weight to highly-cited articles. To calculate the g-index: "[Given a set of articles] ranked in decreasing order of the number of citations that they received, the g-index is the (unique) largest number such that the top g articles received (together) at least g² citations" (from Harzig's Publish or Perish Manual).

Journal-Level Metrics

Journal Impact Factor: The Journal Impact Factor is a measure of the frequency with which the average article in a journal has been cited in a given year. The calculation is based on a two-year period and involves dividing the number of times articles were cited by the number of citable items (articles, reviews, etc.). A Journal Impact Factor of 2 means that, on average, articles in the journal published over a period of two years have been cited two times. An example of how to calculate the impact factor for a Journal for 2015 is below:

Eigenfactor Score: A journal's Eigenfactor Score is a measure of the journal's total importance to the research community. The Eigenfactor Score measures the number of times articles from a journal published in the past five years have been cited in a given year. Like the Impact Factor, the Eigenfactor Score is essentially a ratio of the number of citations to the total number of articles. However, Eigenfactor ranks the overall impact of a journal rather than the impact of articles within that journal.

Article-Level Metrics

Altmetrics: Altmetrics are non-traditional bibliometrics proposed as an alternative or complement to more traditional citation impact metrics, such as journal impact factor and h-index. Altmetrics provide a way to measure mentions, social media posts, downloads, comments, and use of scholarly work in non-academic discussion venues.

From the Executive Summary: "This report details the results of an exploratory case study investigating how researchers responded to a range of quantitative metrics....This paper argues that metrics can be used as a tool for researchers, but should be understood in the context of non-quantitative measures. Metrics alone cannot determine how impactful a researcher’s contribution may be."